Liquid cleaning and maintenance composition especially for dishwashers

ABSTRACT

A liquid, aqueous or aqueous-alcoholic cleaning and maintenance composition, especially for dishwashers, consisting essentially of: 
     (a) from 5% to 50% by weight of a water-soluble, organic monocarboxylic or polycarboxylic acid having from 2 to 6 carbon atoms, optionally substituted with hydroxyl groups, 
     (b) from 3% to 20% by weight of a water-soluble polyhydric alcohol, 
     (c) from 0.1% to 10% by weight of a low-sudsing nonionic tenside, 
     (d) from 0 to 5% by weight of customary additives selected from the group consisting of odorants, dyes, dissolving intermediaries and corrosion inhibitors, 
     (e) from 0 to 30% by weight of a water-miscible monohydric alcohol having from 2 to 4 carbon atoms, and 
     (f) the remainder to 100% by weight of water, based on the total weight of the composition.

BACKGROUND OF THE INVENTION

In the area of door sealings, hose connections and low water zones ofmechanical dishwashers, that is, where the surfaces of the interior ofthe dishwasher are not exposed to the direct and intensive operatingpressure spray of the cleaning liquor, soil is frequently deposited inthe course of time. This soil consists mainly of finely-divided fattyfood residues.

Occasional unavoidable troubles in the ion-exchange system of thedishwasher water supply, which serve to soften the water used, or theconsistent underdosing of the dishwasher detergents by the user alsocause increasingly deposits of a mixture of calcium from hard water andresidues of the detergent on the inner surfaces of the machines.

Partly so-called "tempering colors" are formed, as rainbow-coloreddiscolorations of refined steel parts of the dishwasher or of dishes ofrefined steel are called.

These deposits represent an undesired nutrient soil for rottingprocesses, which manifest themselves by an unpleasant odor, particularlywhen the dishwasher is opened after it has not been used for a longtime. Beyond that, hose and sealing materials, particularly at the door,are damaged by prolonged action of these soil deposits.

The commercial powdered alkaline or acid dishwasher detergents or cleanrinse agents are not or only inadequately suitable for cleaning theso-called "problem zones" of dishwashers where soil is particularlylikely to be deposited. These dishwasher detergents are dose into thewashing and rinsing cycle of the dishwashers and are dissolved therein;however, the soiled regions are not touched at all or only briefly bythem. It is, therefore, necessary to clean these zones manually. Thedetergents used for cleaning the dishes are unsuitable for this purpose,since they irritate the skin. Commercial cleansers for hard surfaces arenot suitable either for these special applications, since they containgenerally high-sudsing tensides or surface-active compounds whoseresidues can lead to various troubles in dishwashers.

OBJECTS OF THE INVENTION

An object of the present invention is the development of liquid cleaningand maintenance compositions especially for mechanical dishwashers.

Another object of the present invention is the development of a liquid,aqueous or aqueous-alcoholic cleaning and maintenance composition,especially for dishwashers, consisting essentially of:

(a) from 5% to 50% by weight of an acid having from 2 to 6 carbon atomsselected from the group consisting of alkanoic acids, hydroxysubstituted alkanoic acids, alkane polycarboxylic acids and hydroxysubstituted alkane polycarboxylic acids,

(b) from 3% to 20% by weight of a water-soluble alkane polyol,

(c) from 0.1% to 10% by weight of a low-sudsing nonionic tenside,

(d) from 0 to 5% by weight of customary additives selected from thegroup consisting of odorants, dyes, dissolving intermediaries andcorrosion inhibitors,

(e) from 0 to 30% by weight of a water-miscible alkanol having from 2 to4 carbon atoms, and

(f) the remainder to 100% by weight of water, where the amount of wateris at least 25% by weight, based on the total weight of the composition.

These and other objects of the invention will become more apparent asthe description thereof proceeds.

DESCRIPTION OF THE INVENTION

The present invention concerns a liquid, aqueous or aqueous-alcoholiccleaning and maintenance composition which is characterized in that itcontains:

from 5% to 50%, preferably from 12% to 25%, by weight of a water-solubleorganic monocarboxylic acid or polycarboxylic acid with 2 to 6 carbonatoms in the molecule, substituted, optionally, by hydroxy groups,

from 3% to 20%, preferably 5% to 12%, by weight of a water-solublepolyhydric alcohol,

from 0.1% to 10%, preferably 1% to 5%, by weight of a low-sudsingnonionic tenside, and

from 0 to 5%, preferably 0.1% to 4.5%, by weight of odorants, dyes,dissolving intermediaries and/or inhibitors,

related to the total weight of the aqueous or aqueous-alcoholicsolution.

More particularly, the present invention relates to a liquid, aqueous oraqueous-alcoholic cleaning and maintenance composition, especially fordishwashers, consisting essentially of:

(a) from 5% to 50% by weight of an acid having from 2 to 6 carbon atomsselected from the group consisting of alkanoic acids, hydroxysubstituted alkanoic acids, alkane polycarboxylic acids and hydroxysubstituted alkane polycarboxylic acids,

(b) from 3% to 20% by weight of a water-soluble alkane polyol,

(c) from 0.1% to 10% by weight of a low-sudsing nonionic tenside,

(d) from 0 to 5% by weight of customary additives selected from thegroup consisting of odorants, dyes, dissolving intermediaries andcorrosion inhibitors,

(e) from 0 to 30% by weight of a water-miscible alkanol having from 2 to4 carbon atoms, and

(f) the remainder to 100% by weight of water, where the amount of wateris at least 25% by weight, based on the total weight of the composition.

In addition to at least 25% by weight of water, the composition of theinvention can contain from 0 to 30%, preferably from 15% to 20%, byweight of a monohydric alcohol with 2 to 4 carbon atoms, particularly awater-miscible alkanol having from 2 to 4 carbon atoms, such as ethanol,propanol, butanol and preferably isopropanol.

The water-soluble organic monocarboxylic or polycarboxylic acids with 2to 6 carbon atoms in the molecule, substituted if necessary by hydroxygroups, consist primarily of alkanoic acids, hydroxyalkanoic acids,alkane polycarboxylic acids and hydroxyalkane polycarboxylic acids. Inaddition to acetic acid, preferably polycarboxylic acids which have a Kvalue of >10⁻⁶, related to the first dissociation stage are employed.These are, for example, adipic acid, succinic acid, tartaric acid, malicacid, glutaric acid, and preferably citric acid. Mixtures of these acidscan also be used.

The water-soluble polyhydric alcohols are preferably water-solublealkane polyols having from 2 to 6 carbon atoms and from 2 to 3 hydroxylsin the molecule, such as ethylene glycol, propylene glycol, dipropyleneglycol and preferably glycerin.

In order to increase the detergent power, known low-sudsing nonionictensides are used which are used, too, as components of detergents forthe mechanical cleaning of dishes, suitable are oxide adducts ontohigher molecular weight propylene glycols with molecular weights of 900to 4,000, as well as adducts of 1 to 10 mols of ethylene oxide or 1 to10 mols of ethylene oxide and 1 to 7 mols of propylene oxide onto highermolecular weight fatty alcohols with 10 to 20, preferably 12 to 18,carbon atoms in the molecule, or mixtures thereof, as well as syntheticalcohols of the chain length C₁₂ -C₁₈ produced by oxosynthesis, andcorresponding alkylene oxide adducts on nonylphenols. Preferred are thebiodegradable adducts of ethylene oxide and propylene oxide onto highermolecular weight fatty alcohols, particularly the addition product of 2to 5 mols of ethylene oxide and 2 to 5 mols of propylene oxide onto amixture of C₁₂ -C₁₈ fatty alcohols.

Apart from dyes and odorants, small amounts of about 0.1% to 4.5% byweight of customary dissolving intermediaries for the tensides and/orodorants can be added, e.g., C₁ -C₃ -alkylbenzene sulfonates, especiallycumene-sulfonates, as well as corrosion inhibitors, e.g., a condensationproduct of aldehydes and amines in an acid medium known under the nameof Rodin 58® by Gerhard Collardin GmbH, Cologne, Germany.

The products according to the invention can be added to the unloadeddishwashers in concentrations of 5 to 40, preferably 10 to 25, gm/literin certain intervals, for example, once or twice a month, especially inthe washing or optionally in the rinsing cycle and left there at leastfor about five minutes at an elevated temperature of about 25° to 60°C., but they can also be used manually preferably in concentrated form.

The liquid, acid cleaning and maintenance agents according to theinvention dissolve and remove both the fatty food residues and calciumand detergent residues in dishwashers. Tempering colors too disappear onrubbing. Due to their content of polyvalent alcohols, premature dryingof the agent is prevented. This way not only rubber and plastic seals orconnections are kept soft and elastic, but stubborn stains are softenedand can be easily wiped off, due to the delayed drying.

The following examples illustrate the invention in more detail withoutbeing limitative thereof.

EXAMPLE 1

    ______________________________________                                        Percent                                                                       By Weight                                                                     ______________________________________                                        1.5        An adduct of 2 mols of ethylene oxide and                                     4 mols of propylene oxide onto a technical                                    mixture of C.sub.12 -C.sub.18 fatty alcohols,                      15.0       Citric acid                                                        8.0        Glycerine, anhydrous                                               20.0       Isopropanol                                                        4.0        Dipropylene glycol                                                 0.15       An odorant                                                         50.25      Water.                                                             ______________________________________                                    

EXAMPLE 2

The following composition was mixed together:

    ______________________________________                                        Percent                                                                       By Weight                                                                     ______________________________________                                        3.0      A 1:1 mixture of an adduct of 2 mols of ethylene                              oxide and 4 mols of propylene oxide onto a                                    technical mixture of C.sub.12 -C.sub.18 fatty alcohols                        and an adduct of 5 mols of ethylene oxide and                                 4 mols of propylene oxide onto a technical                                    mixture of C.sub.12 -C.sub.18 fatty alcohols,                        15.0     Citric acid                                                          3.0      Acetic acid                                                          10.0     Ethylene glycol                                                      22.0     Isopropanol                                                          6.5      Corrosion inhibitor, "Rodine 58".sup.®                           40.5     Water.                                                               ______________________________________                                    

EXAMPLE 3

The following composition was mixed together:

    ______________________________________                                        Percent                                                                       By Weight                                                                     ______________________________________                                        3.5     An adduct of 4 mols of ethylene oxide and 2                                   mols of propylene oxide onto a technical C.sub.12 -C.sub.18                   fatty alcohol mixture,                                                6.0     Tartaric acid                                                         3.0     Adipic acid                                                           2.0     Succinic acid                                                         5.0     Glutaric acid                                                         2.0     Citric acid                                                           10.0    Glycerine anhydrous                                                   18.0    Ethanol                                                               0.2     Odorant                                                               50.3    Water.                                                                ______________________________________                                    

EXAMPLE 4 Cleaning Effect

The following test arrangement was used to determine the cleaning effectof the manually applied agent of the invention on rubber or plasticparts of dishwashers:

A plastic test plate of 26×28 cm was employed. Two grams of anartificial soil consisting of a mixture of soot, machine oil,triglycerides of saturated fatty acids and low boiling aliphatichydrocarbons were applied evenly to the plates by means of anapplicator.

A plastic sponge was saturated with 12 ml of the detergent solutionaccording to Examples 1 to 3 to be tested, and moved mechanically overthe test area. After six wiping movements, the cleaned test area washeld under running water and the loose soil was removed. The cleaningeffect, that is, the whiteness of the plastic surface thus cleaned, wasmeasured with a photoelectric colorimeter LF 90 (Dr. B. Lange). Theoriginal clean white plastic surface was used as a white standard. Inthe measurement, this clean surface was adjusted to be 100% and theartificially soiled surface was adjusted to be 0%. The indicated valuesof the cleaned plastic surface must be considered as percent cleaningeffect (% CE). These are mean values from four determinations. With tapwater, a mean value of 21% CE was obtained.

    ______________________________________                                               Example                                                                              % CE                                                            ______________________________________                                               1      71                                                                     2      77                                                                     3      75                                                              ______________________________________                                    

EXAMPLE 5

The result of the mechanical application of the detergent according tothe invention for cleaning the interior of dishwashers was determined inthe form of the calcium dissolving power and of the cleaning power. Tothis end one of the agents according to Examples 1 to 3, at a rate of250 ml, was put into the cleaning cycle of a commercial dishwasher ModelMiele G 540, with a water content of 10.0±0.5 l and a maximum washingtemperature of 55° C.±3° C.

Calcium Dissolving Power

Glass plates 6×12 were covered evenly with a layer of 5 gm of a mixtureof:

    ______________________________________                                        Grams                                                                         ______________________________________                                        80           Calcium carbonate                                                7            Sodium metasilicate, anhydrous                                   4            Magnesium carbonate-hexahydrate                                  2            Gelatin                                                          60           Water                                                            ______________________________________                                    

and dried for one and half hours at 80° C. This resulted in a stable"calcium deposit". Four glass plates each were washed with one of theagents according to Examples 1 to 3 in the dishwasher. The meanpercentual removal of the calcium deposit (calcium dissolving power) wasdetermined by titrimetric determination of the residual amounts ofCa⁺⁺ - and Mg⁺⁺ -ions. The calcium dissolving power effected solely withwater of 55° C. by mechanical removal in the dishwasher was 30%.

    ______________________________________                                                     % Calcium                                                        Example      Dissolving Power                                                 ______________________________________                                        1            75                                                               2            81                                                               3            69                                                               ______________________________________                                    

Cleaning Power

Thirty grams of soil consisting of:

    ______________________________________                                        Grams                                                                         ______________________________________                                        100          Margarine                                                        50           Raw egg (white and yellow)                                       50           Defrosted frozen spinach                                         100          Drinking milk, 1.5% fat content                                  100          Food grade rolled oats                                           280          Mashed potatoes                                                  400          Brown gravy                                                      ______________________________________                                    

where applied in stripes on refined steel surfaces of the interior ofthree dishwashers, Model Miele G 540, by means of a brush and leftdrying for twenty hours at room temperature. Then one agent eachaccording to Examples 1 to 3 was put into the cleaning cycle of thedishwashers and the latter started as usual. Subsequently the result wasjudged by three test persons. The original, new refined steel innersurface was graded as 10 (absolutely clean) and the refined steelsurfaces obtained after soiling as 0. With pure water treatment at 55°C., a cleaning power grade of 5.5 was obtained.

    ______________________________________                                        Example      Cleaning Power                                                   ______________________________________                                        1            8.5                                                              2            9.5                                                              3            8.0                                                              ______________________________________                                    

The preceding specific embodiments are illustrative of the practice ofthe invention. It is to be understood, however, that other expedientsknown to those skilled in the art or disclosed herein, may be employedwithout departing from the spirit of the invention or the scope of theappended claims.

We claim:
 1. A liquid, aqueous or aqueous-alcoholic cleaning andmaintenance composition, especially for dishwashers, consistingessentially of:(a) from 12% to 25% by weight of an acid having from 2 to6 carbon atoms and having a first dissociation stage K value of >10⁻⁶selected from the group consisting of alkanoic acids, hydroxysubstituted alkanoic acids, alkane polycarboxylic acids and hydroxysubstituted alkane polycarboxylic acids, (b) from 5% to 12% by weight ofglycerol, (c) from 1% to 5% by weight of a low-sudsing nonionic tenside,(d) from 0 to 5% by weight of customary additives selected from thegroup consisting of odorants, dyes, dissolving intermediaries andcorrosion inhibitors, (e) from 0 to 30% by weight of a water-misciblealkanol having from 2 to 4 carbon atoms, and (f) the remainder to 100%by weight of water, where the amount of water is at least 25% byweight,based on the total weight of the composition.
 2. The liquidcomposition of claim 1 wherein component (a) is an acid selected fromthe group consisting of acetic acid, citric acid and mixtures thereof.3. The liquid composition of claim 1 wherein component (c) is a nonionictenside selected from the group consisting of adducts of 1 to 10 mols ofethylene oxide onto C₁₀ -C₂₀ fatty alcohols and adducts of 1 to 10 molsof ethylene oxide and 1 of 7 mols of propylene oxide onto C₁₀ -C₂₀ fattyalcohols.
 4. The liquid composition of claim 3 wherein the fattyalcohols have from 12 to 18 carbon atoms.
 5. The liquid composition ofclaim 1 wherein component (c) is an adduct of 2 to 5 mols of ethyleneoxide and 2 to 5 mols of propylene oxide onto C₁₂ -C₁₈ fatty alcohols.6. The liquid composition of claim 1 wherein component (c) is alow-sudsing nonionic tenside selected from the group consisting ofethylene oxide adducts onto high molecular weight propylene glycolshaving molecular weights of 900 to 4,000, adducts of 1 to 10 mols ofethylene oxide onto C₁₀ -C₂₀ fatty alcohols, adducts of 1 to 10 mols ofethylene oxide and 1 to 7 mols of propylene oxide onto C₁₀ -C₂₀ fattyalcohols, adducts of 1 to 10 mols of ethylene oxide onto C_(12-C) ₁₈synthetic alcohols produced by oxosynthesis, adducts of 1 to 10 mols ofethylene oxide and 1 to 7 mols of propylene oxide onto C₁₂ -C₁₈synthetic alcohols produced by oxosynthesis, adducts of 1 to 10 mols ofethylene oxide onto nonylphenol and adducts of 1 to 10 mols of ethyleneoxide and 1 to 7 mols of propylene oxide onto nonylphenol.